Currently, in the research of the Evolved Packet System (EPS) in the 3rd Generation Partnership Project (3GPP), the requirement that non-3GPP access network accesses the EPS is proposed. Non-3GPP access system mainly includes two types of non-3GPP access network, namely, trusted non-3GPP access networks and untrusted non-3GPP access networks. The trusted non-3GPP access networks include the Worldwide Interoperability for Microwave Access (Wimax) network and Code Division Multiple Access (CDMA) 2000 network, etc. The untrusted non-3GPP access networks include the Wireless Local Area Network (WLAN), etc.
When non-3GPP access network accesses the EPS, trusted non-3GPP access network and untrusted non-3GPP access network use different interfaces to connect to Authorization, Authentication and Accounting Server (AAA server) of the EPS. The AAA server is connected to a Home Subscriber Server (HSS) only through one same interface, that is, when the non-3GPP access network accesses the EPS, the AAA server is required to acquire an AV from the HSS through the same interface. In this way, when User Equipment (UE) accesses the EPS through the non-3GPP access network, if an entity in the non-3GPP access network is breached, or an Evolved Packet Data Gateway (ePDG) connected to the untrusted non-3GPP access network is breached, the AV delivered by the AAA server may be stolen by an attacker, so that the attacker applies the AV to other non-3GPP access networks for further attack.